The manufacturing of matrix drill bit bodies involves loading hard matrix particles and a binder metal into a mold and heating the resulting load assembly to melt the binder and facilitate infiltration of the binder metal into the hard matrix particles. Upon cooling, the infiltration process results in a metal-matrix composite that forms a bit body. Flux may be included in the assembly to reduce impurities that form during infiltration and that lead to defects in the resulting metal-matrix composite.